It is sometimes desirable to add plasticizer to TPU formulations to make the TPU softer. The prior art method to add plasticizer to TPU is to melt mix the plasticizer into the TPU using compounding equipment such as twin screw extruders, and the like, or to swell the TPU pellets with the plasticizer in a heated blender. The compounding step involves an extra operation and adds to the cost of making the final composition. Putting the TPU through an additional melt mixing step can also reduce the molecular weight of the TPU polymer. Plasticizers can also have a tendency to bleed out of the TPU composition, which can cause other problems. It has also been observed that TPU products having plasticizer added by conventional methods exhibit slow snap-back when exposed to cold temperatures.
It would be desirable to have a TPU composition that is plasticized without having to go through a compounding step and to improve the cold temperature properties, especially cold snap-back, of the TPU.